1. Field of the Inventions
The present invention relates to a control device for outboard motors, and particularly relates to a control device for a watercraft that has three or more outboard motors mounted on a transom thereof side by side with each other.
2. Description of the Related Art
Some watercraft can have three outboard motors mounted on a transom thereof, in a side-by-side arrangement. Conventionally, such watercraft incorporate three sets of shift and throttle levers, each of which corresponds to a respective outboard motor. However, it can be a burden for the operator to operate six shift and throttle levers in addition to operating a steering device.
Recently, an improved control device for a watercraft that can control the entire shift and throttle operations of three outboard motors with two levers disposed transversely next to each other (see Non-patent Literature 1) has been suggested. For example, the i6000 series, shift/throttle lever for three outboard motors, available from the Teleflex Morse Co., Ltd. (USA) is such a device.
Using such a device, the operator can control operations of the outboard motor located on the right hand side (hereinafter called “starboard side outboard motor”) using the lever positioned on the starboard side, while the operator controls operations of the outboard motor located on the left hand side (hereinafter called “port side outboard motor”) using the lever positioned on the port side. The outboard motor centrally located between the starboard side outboard motor and the port side outboard motor is controlled in accordance with operational conditions of the starboard side outboard motor and the port side outboard motor. That is, if the starboard side outboard motor or the port side outboard motor is controlled to be in a forward mode and the other one of those motors is controlled to be in a reverse mode, the center outboard motor is controlled to be in a neutral mode. If both of the motors are controlled to be in the same mode, the center outboard motor is also controlled to be in the same mode and in the same throttle opening as those of the starboard side outboard motor or the port side outboard motor.
In some cases, during actual control of a watercraft, such as a trolling control, the throttle levers may need to move to a position corresponding to a fully closed position of a throttle valve so that the watercraft can move very slowly at an extremely low engine speed. Under such circumstances, however, such a low speed cannot be obtained, because the total propulsive force of two or three of the outboard motors, while running at their lowest engine speed, is too strong to allow the watercraft to move at the desired speed. For example, even if the operator sets one of the starboard side or port side outboard motors in the neutral mode to eliminate any propulsive force from that motor, so that the watercraft moves with a thrust that is generated by a single outboard motor, the other one of the starboard side or port side outboard motors and the center outboard motor will continuously generate thrust. Thus, the watercraft is not able to move at the extremely low speed that the operator desires to obtain.